Synthesis of a 'true' Weyl semimetal from a semiconductor, (Cr,Bi)₂Te₃

New materials and quantum phases drive electronic, photonics and quantum technologies. The breakthrough synthesis of the semiconductor GaN in the early 1990s gave us the blue LED, used for lighting and power electronics [1]. What would it take for semimetals and topological materials to have such impact? In the case of Weyl semimetals, one problem is that our Weyl materials are not actually semimetals. An intense worldwide effort starting ~2014 to search all known crystalline materials for Weyl physics gave us TaAs [2], CoSi [3], Co₂MnGa [4,5] and Co₃Sn₂S₂ [6,7]. These materials all exhibit conventional metallic resistivity, hosting intrinsic, trivial conduction electrons which obscure the unique Weyl properties. We have now instead used molecular beam epitaxy to dope the topological semiconductor Bi₂Te₃ with ferromagnetic Cr [8,9]. We find that (Cr,Bi)₂Te₃ exhibits a record bulk anomalous Hall angle > 0.5 (the key figure of merit for a magnetic Weyl semimetal) along with non-metallic conductivity, sharply distinct from earlier Weyl materials and conventional ferromagnets. Together with theory, our experiments suggest that (Cr,Bi)₂Te₃ has a semimetallic Fermi surface composed of only two Weyl points, without irrelevant electronic states. Our design principle could be broadened to ‘true’ non-centrosymmetric Weyl semimetals and may serve as a bridge to commercial semiconductor technologies. Improving the crystalline quality should further increase the figure of merit, and could enable a richer exploration of Weyl light-matter interaction, non-linear response and applications to interconnects and THz generation/detection.

[1] I. Akasaki, H. Amano & S. Nakamura. Nobel Prize in Physics (2014)

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[7] I.B. et al. Phys. Rev. Lett. 127, 256403 (2021)

[8] Tokura, Yasuda and Tsukazaki, Nat. Rev. Phys. 1, 126 (2019)

[9] I.B. et al. Nature 637, 1078 (2025)